Advisory Check is a program that reads security advisories for you. It gathers security advisories using RSS, RDF, or XML feeds, compares them against the installed software, and alerts you if you're vulnerable.
A wide variety of package managers can be queried to detect installed software. Remote systems can be monitored by using the integrated SSH, Windows-RPC, and Nmap support.

Alerttail monitors a given file and executes a
list of actions when a user-defined text pattern
has been written to the file. For example, the
user can pop up a GTK notification window when a
certain message is written to a log file. Actions can be alerttail built in actions (GTK notify action, geoipLocalization action, or filtering text action) or a custom user defined shell command action. A Qt 4 GUI frontend helps with configuration.

Aranha is an application that uses an XML-RPC
layer to retrieve information from one or more
servers. The type of information gathered is
implemented via plugins, and can be displayed or
archived in several different ways. The data is
gathered in Round Robin Databases (integrated with
rrdtool) and can be accessed using a XUL interface
available from the system. Plugins are very easy
to write.

Bandwidth Check is a small utility that helps an administrator measure the available bandwidth. In order to make use of this utility, you will need to turn on the chargen service, which is provided in many inetd implementations.

Bartlby is a network and system monitor,
completely written in C, to provide a scalable
framework with the ability to monitor networks of
various sizes. It consists of a core daemon,
several plugins, and a Web GUI (PHP extension).
The core daemon checks (over active/passive TCP)
services/hosts and notifies users in case of
critical service conditions (mail, SMS, ICQ, and
custom triggers are supported). Bartlby provides
an open plugin interface to give every
administrator an easy to use option to extend the
plugin base, and a fully customizable GUI (written
in PHP using a C extension). Nearby everything
can be controlled via an XML interface.

BigDaddy is a program for monitoring servers. It is similar to Nagios, with the added benefit of also monitoring and controlling the crontab (or any scheduled application) across an entire fleet of servers. The application comes in the form of a daemon for monitoring and reporting as well as an easy-to-use Web-based GUI for controlling monitoring, viewing timelines of incidents, filing incidents and graphing statistics. The application is extensible with any sort of monitoring module and notification is based on a five step escalation process.

Blogbench is a portable filesystem benchmark that
tries to reproduce the load of a real-world busy
file server. It stresses the filesystem with
multiple threads performing random reads, writes,
and rewrites in order to get a realistic idea of
the scalability and the concurrency a system can
handle.

BulkWatch is a utility that monitors sendmail's
logs and takes a specified action when an IP has
exceeded your configured maximum settings. You can
specify that users may send X messages in X number
of seconds. Email in excess of that would trigger
an action, which can be any of the following:
display an alert to the screen in foreground mode;
log an alert to syslog; email an alert to a
predefined email address; or run an external
command with the IP and number of messages as
arguments.

CD-ROM Digest is a program that checks a
multi-track CD-ROM. It reports the MD5 digest and
size for each track on a CD-ROM. The digest is
done as the track is read, without dumping CD-ROM
data on the hard drive. This tool helps users that
are burning a multi-track CD-ROM to check the
result.